Phases, Eclipses, and Tides

Chap 15 Sec 3

Essential Questions – Chap15 Sec 3

1. What causes the phases of the moon?

2. What are solar and lunar eclipses?

3. What causes the tides?

Motions of the Moon• The moon rotates on its axis and

revolves around Earth.• The changing relative positions

of the Earth, sun, and moon cause the moon to appear to change shapes – we see the different phases of the moon.

• The moon revolves around Earth. It takes the moon about 27.3 days to revolve around Earth.

• The moon rotates on its axis in about the same time that it revolves around Earth. For this reason, we only see one side of the moon.

• A year and a day on the moon would be the same!!• As the moon and Earth move, their positions change

in relation to each other. Their positions also change in relation to the sun.

Full Moon

• The changing relative positions of the moon, Earth, and sun cause the phases of the moon, eclipses, and tides.

Phases of the Moon• The moon does not give off its own light. The

moon reflects light from the sun.• The moon appears to have different shapes at

different times. These different shapes of the moon that you see are called phases.

• As the moon revolves around Earth, you see the moon from different angles. You cannot always see all of the part of the moon that is lit by the sun.

• The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth.

• It takes 29.5 days for the moon to go through all phases.

The Dark Side of the Moon

• We often think of the “dark side” of the moon as the side that faces away from Earth. – This isn’t always true – only at a certain phase of

the moon!– At some point during 29.5 days, every part of the

moon will be dark.

Full Moon

First Quarter Moon

Waning Crescent Moon

Phases of the Moon

Teacher – explain this diagram.

Essential Question – Answered

1. What causes the phases of the moon?

The changing positions of the moon, Earth, and sun causes the phases of the moon.

Stop here & complete foldable & notes.

Eclipses

• An eclipse (ih KLIPS) is when an object in space comes between the sun and another object. For example, an eclipse occurs when the moon comes between the sun and Earth.

• When the moon’s shadow hits Earth or Earth’s shadow hits the moon, an eclipse occurs.

• Latin words for sun and moon are solar and lunar.

Solar Eclipse

• Solar eclipses occur when the moon moves in a line directly between Earth and the sun, casting a shadow on Earth.

• A solar eclipse happens only during a new moon.

Solar Eclipse

Total Solar Eclipse

• The umbra (darkest part of the moon’s shadow), falls on a small area of Earth.– The sky will become totally dark – you can even see

the stars and the sun’s corona (outer atmosphere of the sun).

– The area in the umbra sees a total solar eclipse. It is a very small place on Earth.

– The next total solar eclipse is on July 22, 2009 and you’ll have to travel to India, China, or parts of Japan to see it!!

Partial Solar Eclipse

• People in the penumbra, or lighter shadow of the moon, see a partial eclipse.– The sun is partially blocked out.– This shadow covers a larger area of Earth. – The next partial solar eclipse is Jan. 26, 2009 – but

you’ll have to go to India!

Lunar Eclipse

• Lunar eclipses occur when the moon passes through Earth’s shadow.

• A lunar eclipse occurs when there is a full moon.

• During a lunar eclipse, Earth blocks sunlight from reaching the moon.

A Lunar Eclipse

These pictures show the moon passing into Earth’s shadow, being covered completely by the shadow, then moving out of the shadow. The red appearance is because Earth’s atmosphere bends some sunlight around Earth onto the moon.

Total Lunar Eclipse

• The moon moves through Earth’s umbra (darkest part of the Earth’s shadow).– You can see the edge of Earth’s shadow on the

moon before and after a total lunar eclipse.– Lunar eclipses are visible to everyone that can see

the moon right then (the dark side of Earth).– The next total lunar eclipse will be on Feb. 21,

2010 and we should be able to see it!

Partial Lunar Eclipse

• Most lunar eclipses are partial.• They occur when the moon passes through a

part of the Earth’s umbra.• The next partial lunar eclipse is on Feb. 9,

2009 but will not be visible to us. Fly out west or to Asia to see it.

• Two other partial lunar eclipse will occur on July 7 and August 6, 2009 and both should be visible to us.

Lunar Eclipse

Student Photos of the Feb. 20, 2008 Total Lunar Eclipse

Essential Question - Answered

2. What are solar and lunar eclipses?– Solar eclipses happen when the moon’s

shadow falls on Earth and from our view, the sun is covered by the moon. Lunar eclipses happen when the moon moves into the Earth’s shadow and the sunlight is temporarily blocked from the moon.

Stop and complete foldable and notes.

Tides

• Tides are the regular rise and fall of ocean water.

• The moon’s gravity causes tides. The force of the moon’s gravity causes ocean water on Earth to move higher in some places and lower in other places.

• The sun’s gravity also pulls on Earth’s ocean waters.

Spring & Neap Tides

• During a new moon, the sun, moon, and Earth are lined up in a straight line. The combined forces of the sun and the moon cause spring tides. A spring tide is the highest possible high tide.

• Sometimes, the sun, moon, and Earth form a right angle. This arrangement produces a neap tide. A neap tide is the lowest possible high tide.

Essential Question - Answered

3. What causes the tides?

Tides are caused by the moon’s gravity pulling Earth’s water towards it.

Complete remaining notes.